Lenses used in eyeglasses or spectacles for treating myopia, hyperopia, astigmatism and presbyopia of a wearer, or used in sunglasses or protective eyeglasses having wrap-around segments designed to shield the eye from incident light, wind and foreign objects in the temporal vision field of a wearer, have certain optical properties corresponding to a set of specifications as described in a prescription for the wearer.
These lenses are usually prescribed to have a front curved lens surface designed to fit a curve profile of frames. As shown in FIG. 9, for a minus lens 900 with a front curved lens surface 910, the lens edge 920 is thicker than the other area of the lens 900. The larger the front base curve of a minus lens is, the thicker the lens edge of the minus lens is. For example, for a lens with a minus prescription of −4.00 sphere, if the lens has a front base curve of 2.00, the back surface curve of the lens would be of 6.00. If the lens has a front base curve of 4.00, the back surface curve of the lens would be of 8.00. The edge thickness of the lens with the front base curve of 4.00 is larger than that of the lens with the front base curve of 2.00. Traditionally, a patient with a strong minus prescription needs a lens with a very thick edge. Therefore, traditionally the myopia patient will use flatter ophthalmic frame base curve to reduce lens thick edge.
The large thickness at the edge of a lens may have a number of disadvantages such as obscuring wearer's views at wide angles, unappealing appearance, increasing the lens weight, and so on.
Additionally, conventional prescription lens is almost impossible to match with sunglass frame since most of sunglass frame use base curve 6 or 8, whereas conventional minus lens is using base curves between 2 and 4. For instance, for a minus lens of −4.00, its thickness will be extremely thick if the frame base curve is about 6.00 (so as to lens) and lens back side curve shall be cut at a base curve 10 regardless of solution of inadequate bevel matching attempt.
Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.